Shovel dippers are formed with teeth at their leading edge and a dipper door that normally closes the rear of the dipper to hold earth and other materials that are loaded into the dipper by the action of the shovel. The dipper door must be held closed while the dipper is being loaded and while the load in the dipper is swung to a deposit point. At that point, the dipper door is opened to allow the contents of the dipper to empty. Typically, the locking of the dipper door has been accomplished by a mechanical latch proximal a cutting face of the dipper. The mechanical latch holds the door in a closed position, and is released by a cable or trip wire rope to allow the door to swing open under its own weight and the weight of the contents of the dipper. The door is relatched by allowing it to swing closed by virtue of its own weight and the changing attitude of the dipper as the dipper rotates back in preparation for its next loading cycle. An example of such a mechanical latch is found in U.S. Pat. No. 5,815,958 issued Oct. 6, 1998, for “Excavator Dipper Latch Assembly Having Removable Tapered Latch Bar.”
The existing latching mechanisms include a latching keeper and striking plate which is typically located on the front wall of the dipper in order to engage a latch bar mounted within the confines of the dipper door. The front wall of the dipper forms the cutting face of the dipper and is subjected to extreme abuse as the dipper cuts into the earth. The existing mechanical latching mechanisms are subjected to false door release or failure to latch due to fouling caused by rocks and dirt being lodged into the latchkeeper mechanism. Moreover, the constant abuse caused by the latch mechanism being located in the path of material flow results in excessive wear and resulting high maintenance costs and efforts.